knoppix@Microknoppix:~$ perl -E '
> $line = q{(a) Line 1. (b) Line 2. (c) Line 32. (d) Line 42.};
> @arr  = split m{(?=\([a-z]\))}, $line;
> say qq{>$_<} for @arr;'
>(a) Line 1. <
>(b) Line 2. <
>(c) Line 32. <
>(d) Line 42.<
knoppix@Microknoppix:~$